This invention relates generally to medical device delivery systems and, in particular, to a joint for melt-bonding sheaths, catheters, and tubular devices (and methods of forming the melt-bonded joint) for medical device delivery systems that have a host of uses, including, for example, the deployment of a self-expanding implantable prosthesis at selected locations inside a patient's body. The invention may also be used, however, with a balloon expandable and non-expanding implantable prosthesis. In addition to being used with a rapid insertion delivery system, the invention may be used in an “over-the-wire” delivery system, so both systems will be described below.
By way of background, stents are configured to be implanted into body vessels having a passageway in order to reinforce, support, repair, or otherwise enhance the performance of the passageway. The term “passageway” is understood to be any lumen, channel, flow passage, duct, chamber, opening, bore, orifice, or cavity for the conveyance, regulation, flow, or movement of bodily fluids and/or gases of an animal. As an example, stents have been used in the passageways of an aorta, artery, bile duct, blood vessel, bronchiole, capillary, esophagus, fallopian tube, heart, intestine, trachea, ureter, urethra, vein, and other locations in a body (collectively, “vessel”) to name a few.
One type of stent is self-expanding. For a self-expanding stent, the stent is resiliently compressed into a collapsed first, smaller diameter, carried by the delivery system, and due to its construction and material properties, the stent expands to its second, larger diameter upon deployment. In its expanded configuration, the stent exhibits sufficient stiffness so that it will remain substantially expanded and exert a radially outward force in the vessel passageway on an interior surface of the vessel. One particularly useful self-expanding stent is the Z-stent, introduced by Cook Incorporated, due to its ease of manufacturing, high radial force, and self-expanding properties. Examples of the Z-stent are found in U.S. Pat. Nos. 4,580,568; 5,035,706; 5,282,824; 5,507,771; and 5,720,776, the disclosures of which are incorporated in their entirety. The Zilver stent, introduced by Cook Incorporated, is another particularly useful self-expanding stent due to its nitinol platform and use of the Z-stent design properties. Examples of the Zilver stent are found in U.S. Pat. Nos. 6,743,252 and 6,299,635, the disclosures of which are incorporated in their entirety.
Many delivery systems employ a tubular catheter, sheath, or other introducer (individually and collectively, “catheter”) having first and second ends and comprising a lumen for receiving the wire guide. Optionally, these delivery systems may fit through a working channel within an endoscope or an external accessory channel device used with an endoscope.
Generally stated, these delivery systems may fall within two categories. The first category of delivery systems to have been used, and consequently the first to be discussed below, is commonly referred to as an “over-the-wire” catheter system. The other category of delivery systems is sometimes referred to as a “rapid exchange” catheter system. In either system, a wire guide is used to position the delivery system within a vessel passageway. The typical wire guide has proximal and distal ends. A physician inserts the distal end into the vessel passageway, advances, and maneuvers the wire guide until the distal end reaches its desired position within the vessel passageway.
In the “over-the-wire” catheter delivery system, a physician places the catheter over the wire guide, with the wire guide being received into a lumen that extends substantially through the entire length of the catheter. In this over-the-wire type of delivery system, the wire guide may be back-loaded or front-loaded into the catheter. In front-loading an over-the-wire catheter delivery system, the physician inserts the distal end of the wire guide into the catheter's lumen at or near the catheter's proximal end. In back-loading an over-the-wire catheter delivery system, the physician inserts a distal portion of the catheter over the proximal end of the wire guide. The back-loading technique is more common when the physician has already placed the wire guide into the patient, which is typically the case today. In either case of back-loading or front-loading an over-the-wire catheter delivery system, the proximal and distal portions of the catheter will generally envelop the length of the wire guide that lies between the catheter first and second ends. While the wire guide is held stationary, the physician may maneuver the catheter through the vessel passageway to a target site at which the physician is performing or intends to perform a treatment, diagnostic, or other medical procedure.
Unlike the over-the-wire system where the wire guide lies within the catheter lumen and extends substantially the entire length of the catheter, in a novel “rapid insertion” catheter delivery system described in application Ser. No. 60/663,034, the wire guide occupies a catheter lumen extending only through a distal segment of the catheter. The so-called rapid insertion system comprises a system proximal end, an elongate flexible middle section and a system distal end that is generally tubular.
The system distal end, in general, comprises an inner guide channel member sized to fit within an outer guide channel member that is substantially axially slideable relative to the inner guide channel member. The outer guide channel member and inner guide channel member further have entry and exit ports defining channels configured to receive a wire guide. A port includes any structure that functions as an entry or exit aperture, cutout, gap, hole, opening, orifice, passage, passageway, port, or portal, while a guide channel is understood to be any aperture, bore, cavity, chamber, channel, duct, flow passage, lumen, opening, orifice, or passageway that facilitates the conveyance, evacuation, flow, movement, passage, regulation, or ventilation of fluids, gases, or a diagnostic, monitoring, scope, other instrument, or more particularly a catheter or wire guide.
A wire guide may extend from the outer and inner member entry ports, through the outer and inner member guide channels, and exit the distal end at or near a breech position opening located at or near a transition region where the guide channels and exit ports are approximately aligned relatively coaxially to facilitate a smooth transition of the wire guide. Furthermore, the outer guide channel member has a slightly stepped profile, whereby the outer guide channel member comprises a first outer diameter and a second smaller outer diameter proximal to the first outer diameter and located at or near the transition region.
The system distal end also has a self-expanding deployment device mounting region (e.g., a stent mounting region) positioned intermediate the inner guide channel member entry and exit ports for releasably securing a stent. At the stent mounting region, a stent is releasably positioned axially intermediate distal and proximal restraint markers and sandwiched transversely (i.e., compressed) between the outside surface of the inner guide channel member and the inside surface of an outer guide channel member.
Turning to the system proximal end of the rapid insertion delivery system, the proximal end, in general, comprises a handle portion. The handle portion has a handle that the physician grips and a pusher stylet that passes through the handle. The pusher stylet is in communication with—directly or indirectly through intervening parts—the inner guide channel member at the distal end. Meanwhile, the handle is in communication with—directly or indirectly through intervening parts—the outer guide channel member at the distal end. Holding the pusher stylet relatively stationary (while, for example, actuating the handle) keeps the stent mounting region of the inner guide channel member properly positioned at the desired deployment site. At the same time, proximally retracting the handle results in a corresponding proximal movement of the outer guide channel member relative to the inner guide channel member to thereby expose and, ultimately, deploy the self-expanding stent from the stent mounting region. At times, a physician may need to deploy a second self-expanding stent by withdrawing the system from the proximal end of the wire guide. The physician may then reload the catheter with additional stents, and if that is not an option the physician may load another stent delivery system with an additional stent, onto the wire guide. Also, the physician may withdraw the stent delivery system altogether and replace the delivery system with a catheter or different medical device intended to be loaded onto the wire guide.
The delivery system in the rapid exchange delivery system further comprises an elongate flexible middle section delivery device extending intermediate the system proximal end and the system distal end. The middle section delivery device comprises an outer sheath and an inner compression member having first and second ends associated with the system distal end and system proximal end, respectively.
More particularly, the outer sheath first end may be coterminous with or, if separate from, may be associated with (e.g., joined or connected directly or indirectly) the distal end outer guide channel member at or near the transition region, while the outer sheath second end is associated with the handle at the system proximal end. The inner compression member first end is associated with the distal end inner guide channel member at or near the transition region, while the inner compression member second end is associated with the pusher stylet at the proximal end. Therefore, the outer guide channel member of the distal end may move axially (as described above) and independently relative to an approximately stationary inner guide channel member of the system distal end and, thereby, deploy the stent.
Before the novel “rapid exchange” catheter delivery system described in application Ser. No. 60/663,034 and the present invention, the ways of associating an outer sheath distal end and an outer guide channel member second end at a transition region has been to use glue, adhesives, and the like (collectively, “glue”), or to use a subassembly (or insert) that attaches at a proximal end to the outer sheath and attaches at a distal end to the outer guide channel member. One must choose the right glue, however, to join dissimilar materials, and glue must cure, thereby increasing the total processing (fixture) time in the application and assembly of the device. Furthermore, mating the subassembly to the outer sheath and outer guide channel member may be a time consuming and arduous task, one that requires preparation of a mold for a molding step. Moreover, subassemblies typically vary in strength and integrity depending on the joined materials having incongruous mating surfaces and, thereby, point attachments that could cause joint failure due to inadequate stress distribution. In addition, subassemblies typically are more rigid than the materials it joins, so the transition region is liable to kink and to not bend uniformly as the distal end of the outer body navigates a tortuous path within the vessel passageway.
The melt-bonded joint of the present invention solves these and other problems by joining the outer sheath distal end and the outer guide channel member second end at a transition region in a way that provides a breech position opening located at or near the second end of the outer member with a thermal mechanical melt bond that cures relatively fast and uniformly to distribute the stress across the entire bond and provide substantially uniform flexibility.
Therefore, it would be desirable to have a melt-bonded joint for joining sheaths for use with a delivery system for self-expanding devices such as stents, prosthetic valve devices, and other implantable articles inside a patient's body as taught herein, and methods of forming the melt-bonded joint.